1. Field of the Invention
The present invention relates to a method and apparatus for generation of power and heat from fuels employing a pressurized fluidized bed reactor.
2. Brief Description of the Background of the Invention Including Prior Art
A generation of power and heat is generally provided by thermal power plants, which can be distinguished substantially by their combustion techniques. Initially, the technology of the power and heat generation has developed in this context from the grate firing, where coal is combusted in a fixed bed of to coal dust firing, where entrained coal is combusted. The fluidized bed combustion can be placed in between the two mentioned firing methods. A fluidized bed firing occurs when the gas velocity of the air stream directed from below at the bed material increases to such an extent that the packed bed initially transfers into a suspended state and with further increasing gas velocity transfers into a more or less turbulent motion..sup.(X) The fluidized bed firing can be performed under atmospheric conditions or at elevated pressures. The pressurized fluidized bed firing has the advantage that the plants can be constructed as very compact units. FNT (X)The bed material in al fluidized bed combuster does not necessarily consist of the fuel alone, enstead, usually inert material like sand, limestone, ash etc. is used and the fuel, be it solid, liquid, or gaseous is dispersed in the bed material and tehn combusted with the fluidizing air stream.
There is presently very little known about the operation of fluidized bed firings under pressurized conditions in connection with a gas turbine plant. Pressure operated pilot plants are presently in the planning stage, are before the start-up operation or are on a trial basis.
It has been suggested that for power and heat generation from coal by way of a pressure operated fluidized bed firing the intake air is pressurized by a compressor of the gas turbine to the operating pressure and is then fed in two streams to the fluidized bed combustion chamber. One partial stream is directly fed to the fluidized bed as combustion air and the other partial stream is passed through a heat exchanger immersed into the fluidized bed firing. The combustion gas having a temperature of about 860.degree. C. is purified in an electrostatic filter and is united with the hot air from the heat exchanger before entering the gas turbine. The heat remaining in the expanded gases is extracted via a waste-heat exchanger and the waste gases are then fed to a chimney (VGB Kraftwerkstechnik 59 (1979), copy 8, page 636, right column, last paragraph to page 637, left column, paragraph 1 and FIG. 7).
The purification of the hot gas is particularly difficult in these conventional processes. Available for this purpose are electrostatic precipitators, cyclones, bag house filters or granular bed filters and in all types of dust deposition apparatus the high temperature of the smoke gas of about 860.degree. C. is an aggravating factor..sup.(XX) FNT (XX)The term smoke gas is used here throughout to refer to the gaseous combustion products. It is not intended to indicate that theses gases necessarily contain achially smoke, fume or soot etc.
In addition, in the known processes the hot gases have to be conducted through corresponding hot gas pipes to the individual aggregates of the gas turbine plant with a pressure operated fluidized bed firing. For this purpose expensive installations of tubing conduits are required manufactured either from high-alloy Cr-Ni-steels or with a refractory lining and inner tube or through air cooled double jacket tubes, if the smoke gases of temperatures of about 860.degree. C. are to be passed through.